After an uncut spectacle lens is edged to a lens shape (i.e., the edge of an uncut lens is profiled), it is necessary to judge whether or not the lens has been machined according to a desired machining shape data. For this purpose, there is a conventional art of measuring a peripheral shape and a circumference of a machined lens with use of the lens shape measuring apparatus as disclosed in Patent Document 1.
In the lens shape measuring apparatus as disclosed in Patent Document 1, the lens is rotated with engaging a groove of a stylus (probe) with a bevel at the periphery of the lens which is rotatably held by the holding axis such that the groove is pressed to the bevel, an amount of movement of the stylus that moves in the radial direction and in the vertical direction of the lens is detected at certain angles, and a peripheral shape of an entire circumference of the lens is measured based on this amount. In addition, the circumference of the lens is also calculated based on the measured data.
Further, there is an art as disclosed in Patent Document 2 for measuring a contour shape of a lens according to a non-contact technique. In Patent Document 2, after the lens is roughly machined, a line-shaped laser beam is irradiated on an edge surface of the lens, whereby a line of the laser beam is displayed on a lens surface, an image of the line which is displayed is taken with a video camera, and a peripheral shape data of the lens (a width and position of the edge surface) is measured through image processing. Next, finish machining is applied based on the thus acquired shape data, and a bevel is formed on the lens edge surface.    [Patent Document 1] Japanese Patent Application Laid Open No. H6-175087    [Patent Document 2] US Patent Publication No. 6749377